DESCRIPTION: The current training proposal is part of a larger project investigating the development and neurobiological basis of spontaneous stereotyped behaviors in deer mice. This work represents an animal model of Stereotypic Movement Disorder and thus will be a close complement to our studies of stereotypy and related repetitive behavior disorders in individuals with developmental disabilities. Stress has been assumed to play an important role in the pathogenesis and expression of abnormal repetitive behaviors in various clinical populations as well as animals reared or housed in adverse environmental circumstances. Unfortunately, few data are available to test such an assumption. Thus, the present project will test directly the role of stress in the pathogenesis and expression of stereotyped behavior. The first approach to this problem will be to assess the effect of increased stress responsiveness on the development of spontaneous stereotypy in deer mice. This involves increasing the stress responsiveness of deer mice through extended maternal separation and assessing the development of stereotyped behavior. The second aim is to assess indices of stress responsiveness in stereotypic and non-stereotypic deer mice. This aim involves assessing stress-induced alterations in HPA axis and dopamine function in both stereotypic and non-stereotypic mice. In order to understand more fully the role that glucocorticoid and dopamine function play in the pathophysiology of stereotypy, glucocorticoid receptor mRNA expression in hippocampus and dopamine transporter densities in dopamine terminal fields will also be compared in stereotypic and non-stereotypic deer mice